1. Field of the Invention
The present invention relates to a passenger seat air bag system disposed in a portion of an instrument panel in front of a front passenger seat of a vehicle.
The present application is based on Japanese Patent Applications No. Hei. 10-373695 and 10-373726, which are incorporated herein by reference.
2. Description of the Related Art
In the conventional passenger seat air bag system, when an air bag was inflated and unfolded, inflating gas was introduced into the air bag through a gas inlet so that the air bag projected from a portion of an instrument panel and inflated toward the rear side of a vehicle along a wind shield inclined to the front side.
However, there were some cases where it was demanded to reduce the inflating speed of the air bag toward a passenger sitting on the passenger seat, that is, the inflating speed of the air bag toward the rear side of the vehicle.
To meet this demand, there is such a proposal that a flow control cloth is provided inside an air bag so as to cover a gas inlet so that the flow control cloth closes the opposite sides of the air bag in the left/right direction of a vehicle while the flow control cloth leaves the opposite sides of the air bag in the front/rear direction of the vehicle opened (see Japanese Patent Publication No. Hei. 9-263203).
With such a flow control cloth provided in an air bag, when the air bag is to be inflated and unfolded, the inflating gas introduced into the air bag branches into front and rear flows by the presence of the flow control cloth, so that the air bag is unfolded quickly in the front/rear direction. Then, the front portion of the air bag projects toward the rear side of the vehicle along the wind shield. On the other hand, the rear portion of the air bag projects toward the rear side of the vehicle along the upper surface of the instrument panel.
Thus, at the beginning of the unfolding and inflation of the air bag, the air bag inflates toward the rear side of the vehicle with a wide angle spread vertically to thereby occupy a space between the inner surface of the wind shield and the upper surface of the instrument panel. Thus, the air bag moves toward the rear side of the vehicle while spreading its passenger-side portion as a face broadly, so that the speed of the inflation toward the rear side of the vehicle can be reduced.
When such a flow control cloth is provided, the flow rate of the inflating gas flowing into the air bag is preferably set so that the flow rate on the front side is larger than that on the rear side.
That is, if the amount of the inflating gas flowing to the front portion of the air bag is increased, it becomes easy to dispose the front portion of the air bag on the upper side along the wind shield in the initial stage of the unfolding and inflation of the air bag so that the rear portion of the air bag can be located along the upper surface of the instrument panel. As a result, the air bag can be inflated so that the surface facing a passenger at the time of the unfolding and inflation of the air bag is disposed vertically. Accordingly, even if the passenger is bound during the unfolding and inflation of the air bag, the force with which the air bag presses the passenger can be restricted preferably.
To control the flow rate of the inflating gas, it can be considered that the length on the front edge side of the flow control cloth is made long while the length on the rear edge side of the cloth is made short, so that the front-side opening is made larger than the rear-side opening which openings are provided inside the air bag by the flow control cloth.
However, when the flow control cloth is thus disposed inside the air bag in a manner so that the length on the front edge side of the flow control cloth is made long while the length on the rear edge side of the cloth is made short, a great volume of materials for the flow control cloth is required. In addition, the flow control cloth becomes so long that it becomes difficult to perform the working of setting up the flow control cloth by stitch or the like.
In addition, the air bag of the passenger seat air bag system was folded so that the ceiling wall portion side opposite to the gas inlet was made close to the gas inlet side. The air bag was fixedly received in the case while being folded by horizontal folding by which the front and rear opposite edges were made close to each other near the center and vertical folding by which the left and right edges were made close to each other near the center.
In folding the air bag, there was a case where the front portion was folded in the form of bellows at the time of the horizontal folding (see Japanese Patent Publication No. Hei. 7-291068).
In the case where this front portion is folded in the form of bellows, the front portion can indeed unfold quickly compared with the case of roll folding or the like when the inflating gas is introduced into the air bag, but the force with which the front portion collides against the wind shield becomes larger.
Further, at the time of unfolding and inflation, the air bag is unfolded and inflated toward the vehicle rear side along the wind shield. Therefore, the vicinities of the front edge of the air bag move toward the vehicle rear side while rubbing on the wind shield over a long distance. As a result, there is a fear that the air bag is damaged.